A 45-year-old man has been interviewed by police under caution after a video of a confrontation at a shop in Peckham went viral and sparked protests.
Video footage of a woman hitting a man with a shopping basket as he appeared to choke her on Monday provoked anger among people in southeast London who objected to the way he had reacted.
Demonstrators gathered outside the shop on Tuesday afternoon after the video was shared on social media.
The row broke out after the woman was denied a refund and tried to take replacement items from the shop.
Officers visited the shop just after 1.15pm on Monday following reports a woman had attempted to steal items and was prevented from leaving by an employee.
A 31-year-old woman who was arrested on suspicion of assault after the confrontation on Tuesday has been released on bail.
The Metropolitan Police has not identified the man who was questioned on Wednesday but said a 45-year-old has been interviewed under caution.
Footage shows a violent confrontation between a man, said to be of Asian heritage, and the black woman.
He then appears to grab her by the throat before restraining her by her arms, as she tries to break free from his grasp.
The man who appeared in the clip on Tuesday told ITV that he had been detaining the woman rather than choking her.
Detective Chief Superintendent Seb Adjei-Addoh, local policing commander for Southwark, said: "I would like to thank local people for their patience as we work to establish the full circumstances around the allegations made.
"We continue to examine various clips of footage that depict small sections of the wider incident and are working to establish what offences were committed and by whom.
"My officers will be patrolling Rye Lane today to provide reassurance to the community, I know that this incident will cause concern and I urge anyone who is worried to speak with their local policing team or with officers on patrol."
London Mayor Sadiq Khan tweeted: "I know Londoners are concerned by the recent events in a shop in Peckham. I'm in touch with the Met Police and am urgently seeking further information."
Sistah Space, a charity which supports women of African and Caribbean heritage, criticised the police for arresting the woman.
They told Sky News: "What we all saw in that video was traumatic. People do not understand how triggering this is to watch, much less to experience.
"This black woman was attacked and there is no excuse for it, to add insult to injury she was arrested and the perpetrator was left alone at the scene of the crime.
"She has been failed by the police and violently attacked by a criminal with no accountability."
The charity also shared footage on Instagram showing women chanting "shut it down, shut it down" outside the shop during the protest.
Activist Sayce Holmes-Lewis posted footage on social media urging people to boycott the store and to assemble outside at 2pm to peacefully protest.
"We hit them in the pocket, that's the only language they understand," he said.
"Emotions can get the better of us sometimes so it's important that we keep a lid on emotions and be very clear on our objective today, which is to make sure that we boycott this store and any other store that is going to treat us in a derogatory manner and disrespectful, and extract money from the community and not put anything back in."
Mr Holmes-Lewis told Sky News: "I went because I wanted to stand in solidarity with black women abused routinely not protected and supported in the way they should be.
"The protest was peaceful, purposeful and looking for a positive outcome that supports the lady in question.
"[The] point of the protest was to showcase people that treat women in this way, it can't be done and we will come out in force to support them and if they continue to do this, will take our business elsewhere."
He added: "The CCTV doesn't make a difference, the man is 6ft 2ins and twice the size of the lady.
"If no one was there filming and no one to back the lady, who knows what was going to happen. There are levels of violence we are not going to accept, doesn't warrant what he did."